Transient or Steady? What do you think?

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 April 9, 2015, 08:45 Transient or Steady? What do you think? #1 New Member   Zhiyi Li Join Date: Mar 2015 Location: Germany Posts: 26 Rep Power: 2 Hallo everyone, I am working on a cyclone simulation with only air inflow at the first place. Do you think I should use steady simulation or transient simulation? Since turbulence and the flow situation is changing after inflow of the air, should I use transient? I used steady af first, even though my minimum othogonal mesh quality is 0.35, I could not get a converged (residual lower than 0.001) result after 5000 times of steady simulation. So I changed to transient after 5000 times of simulation, this time I got converged situation. Do you think the method I used in the last paragraph is applicable? Or should I run the transient simulation at the first place? I am using 'Reynolds Stress Model (seven equation)'. Thank you Best Regards Litchy

 April 9, 2015, 08:50 #2 Member   subhendu Join Date: Jun 2013 Location: kolkata,india Posts: 39 Rep Power: 4 i think transient a you said it is changing with time

 April 9, 2015, 15:35 #3 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 165 Rep Power: 11 Hi, We can get good converged solution with steady state itself. What boundary conditions and discretization method are you using for the simulation? __________________ With regards, JSM

April 10, 2015, 04:09
boundary condition and discretization method
#4
New Member

Zhiyi Li
Join Date: Mar 2015
Location: Germany
Posts: 26
Rep Power: 2
Quote:
 Originally Posted by jsm Hi, We can get good converged solution with steady state itself. What boundary conditions and discretization method are you using for the simulation?

The discretization method I used is velocity and pressure coupling: SIMPLE
Pressure: PRESTO! because of the highly swirl flow
And the other discretization methods keep default.

Boundary condition: Velocity_inlet: 10m/s and turbulent intensity:5%, hydraulic diameter: caulculated from the geometry, around 0.166m
pressure_outlet: others keep default, turbulent intensity:5%, hydraulic diameter:0.2m
The fluid is only air currently.

Solver is pressure based, raynolds stress method-7 equations method.

Do you think there may be some problems with my settings?

Best Regards

Litchy

April 10, 2015, 04:11
#5
New Member

Zhiyi Li
Join Date: Mar 2015
Location: Germany
Posts: 26
Rep Power: 2
Quote:
 Originally Posted by subhsngh i think transient a you said it is changing with time
Well, it is changing first, when you put in the inflow air. But after a while, with the inflow air reach a balance, there is not much changing, I suppose